1. Field of the Invention
The present invention relates to wireless communication technology field. More particularly, the present invention relates to a Multi-Input Multi-Output (MIMO) transmission based method for transmitting and receiving Downlink Control Information (DCI).
2. Description of the Related Art
In the Long Term Evolution-Advanced (LTE-A) system, in order to improve the performance of the uplink, the MIMO technology is adopted for transmitting data. The uplink physical layer transmission technology of the LTE-A is the same as that of the LTE system, but is still based on the Single Carrier Frequency Division Multiple Access (SCFDMA).
Two pieces of important information (i.e. layer number transmitted of the uplink MIMO (hereafter referred as the layer number) and precoding matrix information) need to be indicated in the DCI dispatching the uplink MIMO transmission. According to the present development of LTE-A technology, as for a dual-antenna User Equipment (UE), when the allocated layer number is 1, the number of the precoding matrixes is 6. When the allocated number is 2, the number of the precoding matrix is 1. As for a four-antenna UE, when the allocated layer number is 1, the number of the precoding matrixes is 24. When the allocated layer number is 2, the number of the precoding matrixes is 16. When the allocated layer number is 3, the number of the precoding matrixes is 12. When the allocated layer number is 4, the number of the precoding matrix is 1. According to the present conclusion, as for the dual-antenna UE, 3 bits signaling is used for indicating the allocated layer numbers and the precoding matrixes. Accordingly, as for the four-antenna UE, 6 bits signaling is used for indicating the allocated layer numbers and the precoding matrixes.
Table 1 is an example of a DCI format for dispatching the uplink MIMO transmission, which is similar to that for dispatching the downlink MIMO transmission in the Long Term Evolution (LTE). New Data Indication (NDI) domains, and Modulation and Coding Scheme (MCS) domains (i.e., NDI0, NDI1, MCS0 and MCS1) in the table are set for each Transport Block (TB). When a base station actually transmits two TBs, the NDI and MCS of the two TBs respectively indicate parameters of the corresponding TBs. When the base station merely transmits one TB, the TB is denoted as TB0, the NDI0 and MCS0 corresponding to the TB0 indicate the parameters of the TB0. In addition, when the DCI needs to indicate that another TB is not activated, the TB is denoted as TB1. The NDI and MCS information domains corresponding to the TB1 do not indicate the transmission parameters of the TB1. At present, the indication information of the layer numbers and precoding matrixes of the uplink MIMO transmission is indicated in the precoding information domain of the DCI. At least 3 bits precoding information domain is needed for the dual-antenna UE, and at least 6 bits precoding information domain is needed for the four-antenna UE. As for this method according to the related art, the mode for indicating the layer numbers and precoding matrixes makes the DCI occupy too many signaling overheads.
TABLE 1Information domainBit numberResource allocationUndeterminedMCS (TB0)5MCS (TB1)5NDI (TB0)1NDI (TB1)1TPC2CSI3Frequency modulation indication0 or 1CQI request1Precoding information3 or 6Switching indication0 or 1SRS activation1CRC (C-RNTI)16 
Therefore, a need exists for a MIMO transmission based method for transmitting and receiving DCI, to reduce the signaling overheads of the DCI.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.